Method of drying materials.



PATENTED JUNE 28, 1904. L. GATHMANN. METHOD OF DRYING MATERIALS.

APPLICATION FILED FEB. 9, 1903.

2 SHEETS-SHEET L No MODEL.

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PATENTED yJUNE 28, 1904.

L. GATHMANN. METHOD 0F DRYING MATERIALS.

AAEPLIATION FILED FEB. 9. 1 903.

2 SHEETS-SHEET 2.

N0 MODEL.

UNITEDA STATES Patented June 28, 1904.

PATENT OFFICE.

LOUIS GATHMANN, OF VASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOR OFONE-FOURTH TO ELDRED P. DICKINSON AND SOMERSET R. WATERS,

OF IVASHINGTON,

DISTRICT OF COLUMBIA.

SPECIFICATION forming part of Letters Patent No. 763,387, dated June 28,1904.

Application filed February 9, 1903. Serial No. 142,653.

To all whom t may concern:

Be it known that I, LOUIS GATHMANN, acitizen ofthe United States,residing at Washington, in the District of Columbia, have invented acertain new and useful Method of Drying Vegetable, Mineral, Animal, andCompound Substances, of which the following is a full, clear, and exactspecification.

This invention has relation to the art of 1o drying substances ormaterials in general, whether` organic or inorganic, of natural orartificial provenance. In this art it has been common to make use of aclosed circuit comprising, generally speak-ing, a drying-cham- [5 ber,means to heat the air in the circuit to vaporizing temperature, means tocause the air to circulate in the circuit, and thereby vaporize themoisture in the substance or material contained in the drying-chamber,and

2o a condenser to condense the vapors as they are evolved from thesubstance or material to be dried or substantially dried. In the dryingof more orless bulky materials liable to be injuriously affected whensubjected al a1/trio to a vaporizing temperature and with a view to heatthem through and through before being' subjected to a vaporizing heatand at the same time prevent surface drying it has been proposed tostartthe operation by first producing 3o a vapor-laden atmosphere at a`temperature below the boiling-point of water by causing the air in aclosed circuit to absorbv more or less steam while in circulation insaid circuit andv before it enters the drying-chamber, the mois- 3 5ture-laden atmosphere being then heated while in circulation to avaporizing temperature, the

circulation being kept up until the material to be dried has been heatedthrough and through and has acquired the same temperature as the 40moisture-laden atmosphere and until the latter has become saturated byadditional vapor evolved fromthe material being dried. When this pointhas been reached, the saturated air has been blownout of the circuit andfresh ambient air taken in, the operation being repeated -untilvthematerial has been freed of its moisture and the moisture blown off.

It is obvious that in a method of drying (No specimens.)

such as last above referred to there is not only a great amount of heatlost by blowing it out of the circuit from time to time and reheatingthe ambient air taken in, so thata substantially saturated atmosphere ata vaporizing temperature cannot be constantly maintained in the circuit,while whenever ambient air is taken in the temperature of the vapor--laden atmosphere which may remain in the circuit, as well as thematerial to be dried, becomes chilled and condensation throughout thecircuit is liable to result, necessitating the revaporization of thecondensate and the reheating of the material to the desired degree andabnormally prolonging the operation of drying.` i

In those processes which are based upon 05 the'eirculation of the dryingmedium lin a closed circuit and the condensing of the vapors no meanshave been provided to produce a vapor laden atmosphere in thedryingchamber.

N ow my invention has for its object the combination of the two methodsdescribed, so im-. proved that the loss of heat is minimized and thecondensation of the vapors is regulated relatively to the heat requiredto restore the lost heat to the circulating medium, so as to maintain asubstantially vapor-saturated atmosphere in the drying-chamber nearly tothe ending of the'operation of drying or until the vapors evolved fromthe substanceor ma- SO terial to be dried become insufficient tosaturate the air. I may produce the vapor-laden atmosphere in thedrying-chamber by heating the substance or material and the air thereiny until sufficient vapor has been evolved from said substance ormaterial to be dried, then cause thev vapor-lad en atmosphere tocirculate in the circuit until it is saturated, lower the temperature ofthe saturated air to a condensing temperature after it leaves thedrying-chamber, and restore the lost heat before itagain enters thedrying-chamber, and so regulate condensation relatively to the heatsupplied as to cause the atmosphere to leave the drying-chamber in asaturated condition o5 until near the end of the operation or until thevapors evolved from the material to be dried are insufficient tosaturate the atmosphere,when said vapors may be condensed as fast asevolved until the material is thoroughly dried.

Instead of producing saturation of the air by circulation I may effectthis inthe dryingchamber by means of vapor evolved from the substance ormaterial to be dried and then establish the circulation and proceed withthe condensation as above set forth, or I may produce the initialvapor-laden atmosphere by admitting vapor, as steam, to thedryingchamber, then heat the vapor-laden atmosphere to a vaporizingtemperature, establish the circulation, and proceed with thecondensation as above set forth.

The various modes of procedure described will depend upon the substanceor material to be dried--as, for instance, upon thepercentage ofmoisture contained in such substance or material or the bulk thereof, orbothand also upon the physical' character of the substance or material.

By the described processI am not only enabled to greatly expedite theoperation of drying, but also to prevent surface drying before thesubstance or material is heated through and through to avaporizingtemperature, while the loss of heat is minimized.

Any suitable apparatus may be employed in carrying out my process, andin the accompanying drawings I have shown two forms of apparatus, whichIdo, however, not desire to claim herein, as they form subject-matter ofseparate applications for patents, filed, respectively, October 1, 1903,Serial No. 175, 339, and December l5, 1903, Serial No. 183,952.

In said drawings, Figure 1 is a vertical transverse section on line 66of Fig. 2, which latter is a longitudinal transverse section on line 55 of Fig. 1 of one form of apparatus. Fig. 3 is a Vertical sectionalview on line 3 8 of Fig. 4, which latter' isahorizontal sectional viewon line 7 7 of Fig. 3, parts being shown in dotted lines. Y

Referring to Figs. 1 and 2, A A indicate the vertical walls of theapparatus; E, the roof:l e, the reversely-inclined bottom or iioor,having at its deepest point an outlet-port K in communication with avalved exhaust-pipe K', Fig. 2. In this structure is builtor arranged adryingchamber B of less dimensions and so as to leave a clear space attop, bottom, and on one side. The drying-chamber B has an inclinedbottomA b5 extending from its inner wall nearly to its outer wall, so asto form a port p, which places the drying-chamber in communication withthe housing-space L below it, in which space or chamber L is arranged aheater-condenser D, of any suitable or preferred construction,preferably in the form of a series of parallel tubes connected tosuitable headers at either end and suitably connected with feed andexhaust pipes for feeding a 2 and one of them in full lines in Fig. 1,thev casings F of said fan-blowers having axial intake-ports anddischarge-pipes projecting upwardly and downwardly into flue-sections 7)b3, respectively, each of said discharge-pipes being providccl with avalve or gate, (respectively indicated by the symbols .f and f2.) In thepartition openings are provided controlled by gates F' and F, the formerarranged above the axial intake of the fan-casings F and lthe latterbelow said intakes, whereby I provide means for reversing thecirculation. If, as shown in Fig. 1, the valvesf and gates F" areclosed, valves f2 and gates F being open, air will be taken from theupper flue-section b2, discharged into the lower fine-section b, forcedthrough ports w" at the foot of its inner wall w into thedrying-chamber, thence through ports in its roof controlled by valves J,and by way of flue B back to fluesection 7)?. If, on the contrary,Valves f' and gates FH are open and valves f2 and gates F closed, airwill be taken from the lower iiuesection Z13, discharged into upperflue-section L2, forced through flue B, ports in roof ,7/ ofdrying-chamber B, thence through ports w' at the foot of wall w of saiddrying-chamber back into lower Hue-section 3. In the bottom of the lowerfiueesection 723'are formed ports controlled by dampers G, which alsocontrol the ports w' in wall 'w of the drying-chamber, so that by moreor less opening the dampers ports w will be more or less closed orcompletely closed. 'I am thus enabled to regulate the volume ofvapor-laden air iiowing to the drying-chamber and to the heatingcondensing-chamber L, which forms a by-pass leading from thelowerflue-scction b3 to the lower part of the drying-chamber, or viceversa, and by means of the dampers J, I am enabled to direct the fiow ofvapor-laden air through the drying-chamber, according as one or more ofthe dampers on either side of the central closed dampers are In thedrying-chamber B is arranged a tubular heater or radiator C, whose upperand lower rows of horizontal tubes, which extend the full length of thechamber, are connected to headers, which latter are connected todowntakes, suitable means being provided, as usual, to feed a heatingagent, as steam, to and exhaust said agent from the heater, said upperand lower`rows of tubes being shown IOO IIO

- as arranged above and below the upper and be dried is placed, andbelow said ledge is located the heater condenser DX, supplied with aheating or cooling agent through pipe D and exhausted through pipe D.The lower head of the drier is conical and has connected thereto at itsdeepest point a valved exhaust-pipe K for the discharge of condenl sate.Below the ledge the drying-chamber B'is connected to the intake f of thecasing F of a fan-blower, the outtake f3 of said fancasing beingconnected to the heating-space of a heater CX, to which a heating agent,as steam, is fed through valved pipe C and eX- hausted through pipe C",which may be a return-pipe to the boiler. (Not shown.) The upper head E'of the drier A is connected by pipe P, provided with a cut-off valve V,to the upper end of-the heating-space in heater CX, said pipe P beingswiveled to the heater con-l nection, so that said head E can be turnedoff the heater A', as shown in dotted lines'in Fig.y

4i, for the introduction of the substance or ma-E terial to be driedinto the drying-chamber B'.`

In the construction of apparatus shown in Figs. 3 and 4 the lower partL' of the drying-chamber B also forms a heating condensing-chamber, andsaid drying-chamber can be cut out of the circuit by closing valve V,1n'

view of the fact that the substance or material to be dried willpractically form a bottom for said chamber, through which bottom heatcan, however, pass or rise into the chamber. v

The operation of the apparatus is as follows, reference being moreparticularly had to Figs. 3 and et: After the substance or material hasbeen placed in the drying-chamber B' and the latter .closed and cut outof the circuit by closing the valve V a vapor-saturated atmosphere isproduced in said ydrying-chamber, and this may be done in various ways:

First. By supplying a heating agent to heater-condenser DX and heatingthe substance or material to be dried and the air in the drying-chamberuntil said air has taken up sufiicient vapor to become saturated, or, inother words, tohave reached the dewpoint, a heating agent beingmeanwhile supplied to heater CX. chamber is then established and thesaturated `air caused to circulate in the circuit down- In saiddrying-chamber, below thel therethrough.

The circuit through the drying-` wardly through the drying-chamber andthrough the heating condensing-chamber L', Figs. 3 and 4, thence throughthe fan-blower, heater CX, pipe P, back to drying-chamber B, thetemperature in the heating condensing-chamber having meanwhile beenlowered to condense some of the vapors, the lost heat being restored tothelvapor-laden atmosphere during its passage through the heater CX tomaintain it at a vaporizing temperature, so that it will again becomesubstantially saturated with vapor evolved from the substance ormaterial to be dried during its passage This is continued, thetemperature in the heating condensing-chamber being gradually loweredirtfaccordance with the reduction in the volume of moisture vaporized inthe substance or material, until the vapors evolved therefrom areinsuiiicicnt to saturate the air, when the temperature in the chamber Lis reduced to such a'n extent as to condense the vapors substantially asfast as evolved until. the substance or material is'completelydrieddthat is to say, until condensationy ceases.

Secondly. By heating the substance or material to be dried and the airconiined in the drying-chamber by means of heat radiated from theheater-condenser D until the air confined in the drying-chamber is moreor less laden with vapor, then restablishing the circulation through thedrying-chamber, while the temperature in the heating condensing-chamberremains unchanged, and causing the vapor-laden atmosphere to circulatein the circuit, wherein its temperature is raised to'a vaporizingtemperature by heat from the heater CX, which circulation `is kept upuntil the air becomes saturated with vapor, or, in other words, hasreached the dew point. Then the temperature in the lower part'L of thedrying-chamber is lowered to condense vapor and the condensationcontinued as described under first The mode of procedure described underfirst may be resorted to in the drying of materials or substancescontaining a comparatively large percentage of moisture, while theprocedure under secondly may be resorted to in drying substances ormaterials containing -a comparatively small percentage of moisture.

IOO

Thirdly. By proceeding as above described Y drying of such substances itis of course of great advantage-1n fact, absolutely necessary-.to heatthem through and through to a vaporizing temperature in a vapor-ladenatmosphere to prevent surface drying, or, in other words, to begin thevaporization from 'the interior to the exterior of the substance ormaterialv to be dried, and thus prevent surface drying.

The heating of the material through and through is materially expeditedby the means provided for reversing the flow of vapor-laden atmosphere,as shown in Figs. l and 2.

Having thus described my invention, what I claim as new therein, anddesire to secure by Letters Patent, is-

l. Producing avapor-laden atmosphere in a space containing the substanceto be dried, causing the vapor-laden atmosphere to flew downwardlythrough said space and through a space on a lower level and back againto the first-named space, heating the atmosphere to a vaporizingtemperature during circulation, maintaining the circulation until theatmosphere is saturated with vapor, then lowering the temperature ofsaid atmosphere during its passage through the space on a lower level toa condensing temperature, restoring the lost heat to the atmosphereafter it has left said lower space, and continuing these operations,under exclusion of ambient air, until the substancel is substantiallyfree from vaporizable matter, for the purposes set forth.

2. The method of drying, which consists in causing a drying medium toflow downwardly through a space containing' the substance to be driedand through a second space on a lower level and back to the upper partof the firstnamed space, heating the said medium to a vaporizingtemperature while in circulation, maintaining the latter until themedium is saturated with vapor, then reducing the temperature of thesaturated medium to a condensing temperature during its passage throughthe space on a lower level, restoring the lost heat to the medium afterit has left the lastnamed space, and continuing' these operations underexclusion of ambient air until the substance to be dried issubstantially free from vaporizable matter, for the purposes set forth.

3. The method of drying, which consists in first heating a drying mediumwhile confined in a space containing the substance to be dried, thencausing said medium to fiow downwardly through said space and thencethrough a space on a lower level and back to the upper part of thefirst-named space, maintaining the circulation of the drying mediumuntil it is saturated with vapor, then reducing' its temperature duringits passage through the space on a lower level, to acondensingtemperature, restoring the lost heat to the drying mediumafter it hasleft said lower space and regulating the condensation to maintain thedrying mediumy in a vaporous condition until the substance to be driedis freed from a portion of its vaporizable matter, then condensing thevapers, and performing these operations under exclusion of ambient air,for the purposes set forth.

4. The method of drying, which consists in first heating a drying mediumto a vaporizing temperature while confined in a space containing thesubstance to be dried, then causing the so-heated medi um to flowdownwardly through said space and thence through a space on a lowerlevel and back to the upper part of the first-named space, reducing thetemperature of the mediumto a condensing temperature during its passagethrough said space on a lower level, restoring the lost heat to themedium during its passage through the space containing the substance tobe dried, and maintaining' these operations until said. substance issubstantially free from vaporizable matter, for the purposes set forth.

5. The method of drying, which consists in causing a drying medium tocontinuously flow downwardly through a space containing the substance tobe dried and back to said space, cooling a portion of said medium afterit has moved out of contact with said substance, to condense a part ofthe vapors only, restoring the lost heat to the cooled portion of thedrying medium before it again moves out of' contact with the substanceto be dried, maintaining these operations until said substance is freedfrom a portion of its Vaporizable matter, then cooling all of the dryingmedium after it moves out of contact with the substance to be dried, andrestoring its lost heat before it again moves out of contact with saidsubstance, continuing the latter operations until the substance issubstantially free from vaporizable components, and performing all ofthe recited operations under exclusion of ambient air, for the purposesset forth.

6. The method of drying, which consists in l heating a drying medium toa vaporizing temperature, causing said medium to flow downwardly througha space containing the substance to be dried, thence in part through aspace on a lower level and in part through a by-pass back to the upperpart of the firstnamed space, 'reducing the temperature of the dryingmedium during its passage through said space on a lower level to acondensing temperature, restoring the lost heat to the drying mediumafter it has left said space on a lower level, maintaining theseoperations until the substance to be dried is freed from a portion ofits vaporizable constituents, then causing the entire volume of thedrying medium to fiow from the upper space to the condensing-space andback to the upper part of the upper space until the substance to bedried is substantially free from vaporizable matter, and performingthese operations under exclusion of ambient air, for the purposes setforth.

7. Causing a drying medium to flow downwardly through a space containingthe substance or material to be dried and through a IOO IIO

drying medium, during its passage through the space on a lower level, toa condensing temperature, restoring the lost heat to the drying mediumafter it has left the last-named space, and continuing these operations,under exclusion of ambient air, until the substance or material issubstantially free from vaporizable matter, substantially as set forth.

LOUIS GATHMANN. VitneSSes:

EMIL GATI-IMANN, PAUL GATHMANN.

